One week into the New Year, Hawaiian Electric had to cut power to Oʻahu customers because it didn't have enough electricity to meet the demand.
It was the first power shortfall event on Oʻahu since 2015.
HECO's grid reliability strategy relies on having backup power ready to bring online at any given moment, but HECO Senior Vice President of Planning and Technology Colton Ching said that a series of unfortunate events on Jan. 8 wiped out the utility's reserves.
A number of units were already offline for scheduled maintenance in early January, according to Ching, which is typical — the utility plans repairs for winter months when the demand for power is lower.
Then in the days leading up to Jan. 8, a few other units needed unexpected repairs, and some plants were "derated," meaning they were operational, but couldn't safely increase their output.
Still, on the morning of Jan. 8, Ching said HECO still had sufficient power on hand to meet Oʻahu's demand.
"But over the course of that morning, several things happened," Ching said.
Due to a shortage of reserve generation capacity, we may be forced to turn off power for 30-minute periods across Oahu beginning at about 530p. From 530p to 6p, customers from Pearl City to Waimalu area will experience an outage: https://t.co/meZmnu5o8x. #OahuOutage pic.twitter.com/YTC3iViL4a
— Hawaiian Electric (@HwnElectric) January 9, 2024
First, solar power generation nosedived as a low-pressure system moved over Oʻahu and brought cloud cover and rain.
"(We rely) very heavily on customer-owned solar systems to produce a lot of energy during the daytime," Ching said. Without it, HECO had to rely on its firm generation plants, which primarily burn oil.
Ching said that with the help of energy reserves in utility-scale batteries, the utility had enough to power Oʻahu through the next day. But then the storm brought more surprises.
Power lines connecting one of the units at the Waiau Power Plant to the grid were damaged due to the bad weather, said HECO spokesperson Darren Pai.
Another unit at Waiau was taken out temporarily by flooding, as was H-POWER, the waste-to-energy facility in Kapolei.
With three additional units in need of repair and no clear skies in sight, leaders at HECO calculated that the grid was not going to have enough power to serve the peak load that evening.
"And so that's when we made the decision to call for conservation and to announce that we could be initiating rolling blackouts," Ching said.
What was the role of energy storage?
Utility-scale batteries, including the Kapolei Energy Storage project, which had just started commercial operations a few weeks early, helped HECO weather the storm.
KES has a storage capacity of 565 megawatt-hours of electricity, making it the largest storage project in the state.
Normally, power from batteries comes into play in the evening, when solar power production dips and demand rises as residents return home from work.
The utility needed to tap into those reserves much earlier on Jan. 8 to make up for the deficit of solar power.
Ching estimated that KES was charged up to about 80% of its capacity on the morning of Jan. 8. HECO discharged power from KES, along with reserves from the batteries attached to the Mililani 1 Solar and the Waiawa Solar farms to keep the lights on.
When it became clear that they would be short on power that evening, HECO attempted to recharge the batteries.
But there was only a short window of time in the afternoon in which the grid was producing extra energy that could be stored at KES, and the Mililani and Waiawa batteries could only be charged by their respective photovoltaic systems.
The little bit of electricity HECO was able to squirrel away wasn't enough. Heading into the evening hours when demand was highest, HECO still had several units offline and no banked power.
They ultimately initiated rolling blackoutsthat evening around 8 p.m.
What does the Jan. 8 shortfall tell us about Oʻahu's power grid?
While grid reliability involves several factors, Colton Ching said it boils down to one straightforward principle: "Will the lights stay on? And often will [they] go out?"
So does the shortfall event mean that Oʻahu's grid is unreliable?
Depends on how you look at it, said Richard Rocheleau, director of the Hawaiʻi Natural Energy Institute. Rocheleau has been conducting grid reliability assessments of Oʻahu for HECO since 2021.
He said the national utility standard allowance for shortfall events is about once every 10 years. Given that Oʻahu's last outage of this kind was in 2015, Rocheleau said HECO is operating pretty well within the norm.
Ching said that HECO's current target is no more than one shortfall event every 4.5 years. The utility is working with the Public Utilities Commission to lower that probability to once every decade.
"No one could afford an electric grid with power plants that will never experience a set of conditions that result in a shortfall of power," Ching said.
Rocheleau agrees a reliability strategy that assumes nothing ever breaks or goes wrong is unreasonable, but he does have some concerns about Oʻahu's grid.
One worry is the age of the power plants, which Rocheleau said are some of the oldest in the country.
"That's a very important parameter in terms of what's the likelihood of there being a shortfall in capacity," Rocheleau said.
Older conventional fossil-fuel plants also tend to make up a bigger share of the overall electricity generation on the grid, which means if they go offline, it's harder to make up the difference.
Rocheleau points to the Kahe 4 oil generator that went out of service unexpectedly in July 2022. It produced roughly 90 MW of electricity and didn't return to the grid until fall 2023.
That's exactly the type of situation that will get us into trouble, Rocheleau said, especially while growing pains for new solar projects continue.
"If these older units on Oʻahu fail for whatever reason, will parts be available? Will they be down for extended periods of time?" Rocheleau said, "That, to me ... is the big risk."
